1. Field
This present disclosure relates to forming microspheres, particularly silicon microspheres, through laser, particularly pulsed laser and/or focused laser, irradiation and ablation of a material surface.
2. Background
Lasers have for many years been used to scribe and anneal a variety of materials, including semiconductor materials such as silicon wafers. Randomly sized and shaped ablated material has heretofore been a waste by-product of such activities.
As technologies push the limits of scaling to smaller dimensions, there is a need to engineer materials on the microscale in order to provide unique functionality and capabilities. One field in which this has been demonstrated is photonic devices, in which the need for low-cost products has stimulated a significant amount of research in silicon photonics. Silicon is transparent in the standard ITU optical communication bands, which is a factor in selecting silicon for passive and active optoelectronic devices.
The silicon microsphere shows promise as a building block for silicon microphotonics, a complementary technology to the already well established CMOS microelectronics technology for the realization of future microelectro-photonic integration. Numerous potential applications can be realized by using microspheres, including microlasers, channel dropping filters, optical switching, ultrafine sensing, displacement measurement, rotation detection, high-resolution spectroscopy, and Raman lasers.
Microsphere production is currently utilized in several techniques which are used routinely in the powder metallurgy industry. Unfortunately, many of these techniques are not applicable to silicon sphere production because of contamination and other materials-related problems. Such techniques usually require contact of the molten metal with crucibles, nozzles, or other system parts, and so each such metal object presents a new set of materials contamination and compatibility problems. The materials problems are particularly challenging when the desired product is something approximating the purity of semiconductor grade silicon, which does not tolerate significant impurities for most applications. Further, the current technology is limited because the techniques of forcing molten silicon through a nozzle typically produces spheres having diameters between 250 μm and 500 μm.
There is therefore a need for an apparatus and methods to form microspheres in an easily manufactured, high volume process. Further, there is a need to dispose of scrap wafers generated in the semiconductor fabrication process.
Generally, the techniques described herein are intended to meet the general need for forming microspheres of any ablatable material. The examples provided herein focus on the specific example of semiconductor materials, and more particularly silicon; however, these are given as non-limiting examples.